Been having some issues with the defroster in my 02 Cavalier, when ever i switch from vents to windshield defroster i hear an almost cracking sound, i have looked into the vents and seen that some of the spongy stuff around the selector blower pipe has come loose, will there be any problems if i take that sponge stuff off? ar should i replace it with something similar

Thanks

It's probably a vacuum flap diverting blower air to the defroster. As long as the vents work as they should, this is nothing to be worried about.

2002 Cavalier 2200 5spd

That "sponge stuff" is usually used to help seal around selector doors in the system. It also helps keep them from making noise when they move from one setting to another, so if it's loose, it's probably just the door hitting the housing that you're hearing.
It will probably be difficult to get another material to stick in there, so unless you really object to the noises, I probably wouldn't bother with it.